"Pausing playback of a video or other processing in a background tab is useful to save energy. So only enable this add-on if you can afford it. There are other

"Pausing playback of a video or other processing in a background tab is useful to save energy. So only enable this add-on if you can afford it. There are other ways to detect if a webpage is visible, e.g. onblur/onfocus. This add-on does not disable any of those other ways. So do not assume that this add-on will enhance your privacy." From the Readme of the FF addon.